The present invention relates to electronic apparatus for improving the visual display on a T.V. screen by electronically creating a black matrix or mesh surrounding the individual luminescing dots. In the past, a black and white T.V. picture was a series of horizontal lines of light whose intensity varied along each line. Each horizontal line was separated by a thin, unilluminated area which appeared as a thin black line. Because such a T.V. picture in each field had a series of thin black horizontal lines, one above the other in the vertical direction, the eye of the viewer was forced to integrate the display in the vertical direction. However, because the light spots along the horizontal line ran together, the eye was not forced to integrate horizontally. By creating a series of vertical lines similar to the horizontal lines in a standard T.V. picture, the present invention forces the viewer's eye to integrate the image uniformly in both spatial directions. Such a picture, with the black mesh background, produces a sharper, clearer image and a more viewable display.
Not only does the periodic disruption of a horizontal scan cause a sharper image but the abrupt boundary definitions between light dots helps eliminate phosphor light blooming. In particular, when the video input is blacked out between each pixel of the horizontal display, a large dynamic range signal is less likely to cause phosphor light blooming. When the rate at which the blackout level is switched on and off approximates the video band width of the display system, then the potential for phosphor light blooming is decreased even further.
Previously, black mesh or matrix backgrounds were produced by placing a black grid on the face of the cathode ray tube. This procedure is expensive. The present invention, with the addition of a simple and low-cost, electronic circuit or circuit chip to the electronics of T.V., eliminates the need for a precision manufactured black matrix grid and the labor to install and align it. Although this circuit has its easiest application to black and white televisions which have a continuum phosphor on a screen, it is also adaptable to color T.V. By using an electronic black matrix, such as the present invention imposes, the precision in placing the phosphor dots can be reduced.
A major application of the present invention is in medical diagnostic equipment. This field commonly uses black and white T.V. monitors with a gray scale but demands great visual accuity--accuity not just to the human eye but to cameras which take photographs of the visual display on the T.V. screen. Photographic images from a T.V. screen with the black matrix background are more viewable to the eye and produce an image which is more easily and fully resolved. Such an image also can produce more accurate measurements of distances and sizes. Photographs from T.V. images without the black matrix tend to be striped which produce photographs that are relatively easily resolved perpendicular to the scan lines but which are more difficult to resolve along the scan lines.
A primary use for the present invention is to display the output from ultrasonic diagnostic equipment. Ultrasonic diagnostic equipment is able to make a very precise electronic record of the object scanned by the ultrasonic array. However, this very accurate information can be lost on a T.V. monitor which does not have excellent visual resolution in all directions. The present invention greatly improves the accuracy with which ultrasonic diagnostic equipment can view the internal areas of a patient. The invention makes a great improvement in the viewability of the display very inexpensively. To achieve similar improvement by modifying the ultrasonic diagnostic equipment, in particular the control circuitry or the transducer's array, would require a far greater cost that increases in complexity.